WO2010002974A1

WO2010002974A1 - Uv-based production of chlorine dioxide from chlorate or chlorite

Info

Publication number: WO2010002974A1
Application number: PCT/US2009/049377
Authority: WO
Inventors: Joseph Callerame
Original assignee: Joseph Callerame
Priority date: 2008-07-03
Filing date: 2009-07-01
Publication date: 2010-01-07

Abstract

Chlorate including sodium chlorate is used to produce chlorine dioxide gas upon exposure to ultraviolet radiation in the presence of a suitable catalyst. Chlorine dioxide gas can be used to disinfect, bleach and for a variety of industrial and commercial purposes. A Teflon®-coated UV lamp is optionally used to irradiate a solution of chlorate.

Description

UV-BASED PRODUCTION OF CHLORINE DIOXIDE FROM CHLORATE OR

CHLORITE

Inventor: Joe Callerame

BACKGROUND

[0001] Chlorine dioxide is of considerable industrial importance and has found use as a disinfectant and in the bleaching of wood pulp, fats, oils and flour. Generally, chlorine dioxide is used as a bleaching agent and for removing tastes and odors from water and other liquids. More recently, it has been used as an anti-pollutant. [0002] For several of the established uses of the chlorine dioxide, it is desirable to produce the gas in situ so that the chlorine dioxide, upon formation, can be directly put to use either in gaseous form or, after absorption, in the form of an aqueous solution. In many instances, the use of chlorine dioxide solution rather than in the gaseous form is preferred. Chlorine dioxide is absorbed in water and forms chlorous acid, from which the gas can be readily expelled by heating. The presence of chlorous acid in an aqueous solution indicates a reaction of chlorine dioxide with water.

[0003] Chlorous acid, HClO₂, is stable at low concentrations and is not generally stored long-term as a commercial product. However, the corresponding sodium salt, sodium chlorite, NaClO₂ is stable and inexpensive enough to be commercially available. The corresponding salts of heavy metals (e.g., Ag⁺, Hg⁺, Pb²⁺, and Cu²⁺) and ammonium (i.e., NH₄ ⁺) decompose explosively with heat or shock. [0004] Sodium chlorate (NaClOs) is an oxidizing agent. When pure, it is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 250 ⁰C to release oxygen and leave sodium chloride. Industrially, sodium chlorate is synthesized from the electrolysis of hot sodium chloride solution in a mixed electrode tank: NaCl + 3H₂O → NaClO₃ + 3H₂. It can also be synthesized by passing chlorine gas to a hot sodium hydroxide solution. It is then purified by crystallization. [0005] Sodium chlorite is derived indirectly from sodium chlorate, NaClO₃. First, the explosively unstable gas chlorine dioxide, ClO₂ is produced by reducing sodium chlorate in a strong acid solution with a suitable reducing agent (for example, sodium chloride, sulfur dioxide, or hydrochloric acid). The chlorine dioxide is then absorbed into an alkaline solution and reduced with hydrogen peroxide, H₂O₂ yielding sodium chlorite.

[0006] Chloric acid, HCIO₃, is a colorless substance that occurs only in solution. It is a strong acid and a strong oxidizing agent that decomposes if heated above 40 ⁰C.

Under certain conditions it forms oxygen, water, and the explosive gas chlorine dioxide

CIO₂, under other conditions it forms perchloric acid and hydrochloric acid.

[0007] Perchloric acid, HClO₄, is a volatile, unstable, colorless liquid that is a strong, corrosive acid and a powerful oxidizing agent, especially when hot. It explodes if heated to about 90 ⁰C or on contact with combustible materials. The monohydrate,

HClO₄ H₂O, is fairly stable and forms needlelike crystals that melt at 50 ⁰C. It explodes if heated to 110 ⁰C. The dihydrate, HClO₄ 2H₂O, is a stable liquid that boils at 200 ⁰C.

[0008] Several processes have previously been proposed for producing chlorine dioxide. Attention is thus directed to U.S. Pat. Nos. 3,684,437, 3,695,839,

3,828,097, 3,754,079, 4,874,489, and 4,877,500, all of which are directed to the production of chlorine dioxide or chlorous acid from which the chlorine dioxide can be expelled.

[0009] There exists a need to produce chlorine dioxide gas from a relatively cheaper raw material. Methods and compositions provided herein relate to production of chlorine dioxide gas from chlorate.

SUMMARY

[0010] The present disclosure relates to methods of using chlorate or chlorite to produce ClO₂ gas by ultraviolet (UV) irradiation.

[0011] Chlorine dioxide gas is produced by subjecting a chlorate solution or a chlorite solution to ultraviolet radiation in the presence of a catalyst. Examples of a suitable chlorate include sodium chlorate, potassium chlorate, and calcium chlorate; and examples of a suitable chlorite include sodium chlorite, potassium chlorite, and calcium chlorite. An example of the catalyst is carbon. Other examples of a suitable catalyst include noble metals such as platinum, gold, silver, heavy metals, and others such as mercury and tungsten. Generally, any metal that facilitates or acts like an anode in the presence of UV (accepts the negativity of chlorate) and does not react with chlorine dioxide or the chlorite or chlorate is suitable. The reaction may also be enhanced by the presence of chloride or hydrogen ions. Chloride ions can be introduced in many ways, e.g., by addition of a chloride salt (e.g., NaCl, NaCl₂, KCl, or NH₄Cl) or hydrochloride. Likewise, hydrogen ions can be introduced by addition of an acid such as HCl, CH₃COOH, or H₂CO₃. Alternatively, hydrogen ions can be introduced by bubbling with carbon dioxide (CO₂) into an aqueous solution to form carbonic acid which in turn ionizes to give rise to hydrogen ions. Generally undesirable chlorine is not formed significantly by the reaction, which is a commercial and environmental advantage. The yield of chlorine dioxide obtained by exposing the chlorate solution to ultraviolet radiation is a function of the exposure time, the intensity of the radiation and the concentration of chlorate and the presence of the catalyst in the solution. Since chlorine dioxide gas at higher concentrations has explosive properties, the above parameters are generally chosen such that the concentration of ClO₂ in the reaction mixture does not exceed about 10%. Alternatively, the generated chlorine dioxide gas can be continuously or periodically removed to maintain a desirable concentration in the reaction chamber.

[0012] Chlorine dioxide gas may be generated following general equations shown below as examples: xC10₃ ^~ + H2O → [UV and Carbon] → yC10₂ (g) + 2OH^" (1)

Na⁺ + ClO₃ ^" → [UV, H₂O and Carbon] → ClO₂ (g) + Na⁺ + HCO₃ ^" (2) xC10₃ ^" + H2O + CO₂ → [UV and Catalyst] → yC10₂ (g) + OH^" + HCO₃ ^" (3) xC10₂ ^" + H₂O → [UV and Carbon] → yC10₂ (g) + OH^" (4) xC10₂ ^" + H2O + CO₂ → [UV and Catalyst] → yC10₂ (g) + OH^" + HCO₃ ^" (5)

(x and y can be any integer)

[0013] The chlorine dioxide generation process is advantageously carried out in situ. The chlorine dioxide formed need not be separated from the reaction mixture, but the entire reaction mixture, including the chlorine dioxide formed, may rather, in most instances, be used as a whole since the other components of the reaction may not exert any detrimental influence on the end uses. Also, a chlorine dioxide containing reaction mixture may be removed from the reaction space and transported to a place of use. [0014] Another advantageous feature of the present process is that the reaction parameters can be regulated with ease so that chlorine dioxide free of chlorine is formed. [0015] The UV-lamp in the reaction chamber may be coated with Teflon^® or polytetrafluoroethylene (PTFE) or any suitable non-corrosive layer to enhance the life and the efficiency of the lamp and to minimize undesirable salt deposits. [0016] A method of producing chlorine dioxide includes the steps of introducing a solution of chlorate (e.g., NaClOs) or chlorite (NaClO₂) into a reaction chamber and subjecting the chlorate to ultraviolet radiation in the presence of carbon catalyst. The chlorate concentration is from about 0.1% w/v to about 25% w/v. Suitable chlorate concentrations also include 25% to 45% and 10% to about 50% w/v and 40% to 65% w/v. As long as there is sufficient water for protonation, the chlorate solution or slurry is suitable for chlorine dioxide generation. The chlorine dioxide generated may be less than about 10% w/v, or the generated gas can be continuously removed or stripped and the production of chlorine dioxide is performed in situ. [0017] The ultraviolet radiation is provided by one or more ultraviolet generating lamps, optionally coated with an anticorrosive material. The anticorrosive material is Teflon^® or any other suitable material. The pH may be maintained in a range of about pH 3.5 to about pH 5.0. The chlorine dioxide produced is removed from the reaction chamber and conveyed to a place of use or directly used along with a solution from the reaction chamber. A cation ion-exchange resin may also be used as a reaction chamber for ClO₂ generation using chlorates.

[0018] One or more UV lamps can be positioned such that there exists a time interval between irradiations. The one or more UV lamps can be turned off and on such that there exists a specific period during which there is no irradiation. This cycle of irradiation followed by a pause, enhances the yield of chlorine dioxide. This cyclical irradiation pattern is established by configuring one or more lamps serially or in parallel configuration, such that an incoming flow of precursor is exposed to the one or more lamps in a serial fashion with time intervals or by turning on and off the UV lamps in a periodic mode.

BRIEF DESCRIPTION OF THE DRAWING

[0019] The drawing is provided to illustrate an apparatus used for some of the embodiments of the disclosure. It is envisioned that alternate configurations of the embodiments of the present disclosure maybe adopted without deviating from the disclosure. [0020] FIG. 1 is a diagrammatic rendering of apparatus for producing chlorine dioxide.

DETAILED DESCRIPTION

[0021] While the present disclosure may be susceptible to embodiment in different forms, there is shown in the drawing, and herein will be described in detail, embodiments with the understanding that the present description is to be considered an example of the principles of the disclosure and is not intended to be exhaustive, restrictive in character, or to limit the disclosure to the details of construction, the arrangements of components and methods set forth in the following description or illustrated in the drawing, and that all changes and modifications are incorporated herein.

[0022] U.S. Pat. Nos. 4,874,489 and 4,877,500 describe generation of ClO₂ from sodium chlorite, the disclosures of which are hereby incorporated by reference. International application publication WO 2007/137223 (Callerame) teaches various configurations for generation of chlorine dioxide, the disclosure of which is hereby incorporated by reference in its entirety, as if fully set forth herein. Coil configurations for the reaction vessel and use of EMF to generate chlorine dioxide as mentioned in WO 2007/137223 are incorporated herein by reference. [0023] The reaction process may be carried out generally in an exemplary reactor shown in FIG. 1. The reactor comprises a tubular vessel 1 having a valve-controlled bottom inlet 2 and a valve-controlled top exit 3. The tubular vessel may be made of glass, titanium, a steel alloy, such as known under the name Hastalloy C or any suitable composite material. An ultraviolet radiation source, e.g., one or several quartz lamps 4, is arranged within the space 5 defined by the tubular vessel 1. Although the quartz lamp is shown to have a distinct shape, it will be appreciated that other shapes, such as U-shaped quartz lamps, may also be used. The electrical connections for the quartz lamp are diagrammatically indicated by reference numeral 6. If the wall material of the tubular vessel 1 is UV radiation transmitting, the UV source may be arranged outside the vessel. The UV lamps may be coated with Teflon^® or generic PTFE or any suitable anti-corrosive layer to increase the life and efficiency of the lamp. [0024] In order to enhance and contain the ultraviolet radiation emitted by the lamp, and if the reactor wall transmits UV radiation, it may be advantageous to provide a shiny reflector, such as of aluminum, at the outside of the tubular vessel 1. Such a reflector is generally indicated in the drawing by reference numeral 7. The reflector may be arranged within the reaction space if it has a surface coating resistant to the reactants. [0025] As a general proposition, the reactor wall material may be of the UV transmitting kind if the UV source is arranged outside the reactor space, but may be nontransmitting if the light source is located within the reactor space. The wall may thus be of glass, plastic, steel alloy or titanium, provided the material is resistant to the reactants. As stated, a highly polished aluminum reflector should advantageously be used to contain the intensity of the radiation in the chamber space of the reactor if the material transmits UV radiation.

[0026] Ability to use dilute chlorate mixture with water is an additional advantage of this system for chlorine dioxide generation. The overall reaction process requires less maintenance reduce operating costs.

[0027] The reaction is improved for example 25% by adding a protonating catalyst for example, elemental carbon exposure to UV radiation at 200-280nm. The kinetics of the reaction are also improved as the reaction rate increases with the amount of adsorptive surface of the elemental carbon that is included with the reactants as exposed surface (rod-granular). Carbon is not a reactant, but acts as a catalyst. Suitable UV ranges include 180-300 nm, 220-260 nm, 240-250 nm and 254 nm. Protonation may not be required for the total duration of production process. An initial protonating source may be useful in triggering the catalytic conversion of chlorate to chlorine dioxide.

[0028] In an embodiment, organic acids and inorganic acids or any proton donor that ionize with the NaClO₃ is suitable.

[0029] In an embodiment, extraction of ClO₂ from the reactants is accomplished with for example, air stream (positive pressure) or vacuum (negative pressure) or heat or extreme cooling of the reactants or any other standard procedure to remove gas from a reaction chamber.

[0030] Speed of the reaction is increased as the pH decreases. The oxygen that is released from the chlorate reacts to produce carbonic acid. Surprisingly, the presence of a suitable catalyst (e.g., carbon), ultraviolet radiation is used to convert the readily available relatively inexpensive chlorate to chlorine dioxide efficiently. Use of the catalyst also reduces reaction time and improves the overall efficiency of the chlorine dioxide generation system.

[0031] In an embodiment, the overall reaction of converting a precursor to ClO₂ is enhanced by irradiating the precursor (e.g., NaClO₃ or any suitable precursor to generate chlorine dioxide) serially, wherein a specific "pause" period is maintained during which no irradiation is performed. This series of irradiation followed by a period of no irradiation (e.g., 1/5* to 1/20* the time for irradiation) increases the yield of chlorine dioxide. The serial irradiation or pulsing is accomplished by (i) turning on and off the one or more UV lamps with a specific time interval or by (ii) configuring a plurality of UV lamps positioned such that the incoming precursor for chlorine dioxide generation is exposed serially to the UV lamps, wherein there is a temporal and/or spatial interval between irradiations. Any deposits of sodium if present on the lamp can also be scraped or cleaned intermittently during the process.

[0032] Without being bound by the underlying theory behind the periodic irradiation or pulsed irradiation, it is believed that each exposure to UV excites the precursor molecules (e.g., NaClO₃ or any suitable precursor for UV-based ClO₂ generation), a photon is discharged and ClO₂ is formed by the reactions disclosed herein. The presence of ClO₂ (yellowish) acts as interference for further UV penetration during an extended synthesis phase. Thus, the rate of ClO₂ generation is diminished as the UV exposure continues or toward the later stages in the production. The reaction is not a linear progression, but proceeds more of a parabolic nature showing diminishing returns.

[0033] By giving the irradiated solution a pause from irradiation, allows the reaction to settle (e.g., the overall entropy goes down and the yellow color decreases). This pause allows the solution to once again become "ready" for effective penetration by UV radiation to convert the remaining precursor to ClO₂. The overall reaction is increased significantly by the pulsed irradiation and by repeating this process until a desired yield is achieved. Polarized UV is also suitable for such pulsed irradiation. [0034] The time interval between the irradiation may vary depending on the strength of UV lamps and the duration of the irradiation, the dimensions of the container and the percent yield desired. For example, the pause period may extend from a few seconds to a few minutes. Alternatively, the pause period may be a fraction of the time required for the irradiation. For example, the pause period may vary from l/5^th to about 1/20* or 1/30* of the time required for the irradiation phase. The frequency of the pulses may also vary. The pulsing mode need not be carried out from beginning to end and may be performed towards the later stages of the production. [0035] The inventive method described herein involves the surprising effects achieved by exposing the reactants to a polarized radiation at from about 200-400 nm, preferably 240-360 nm wavelength. The wavelength can be varied about these parameters, however, without limiting the scope of the invention, in one embodiment, increased ClO₂ production is achieved when the polarized UV radiation is held constant at about 254 nanometers. The polarized radiation, such as, for example, polarized UV light may be about 75% polarized or about 80% polarized or about 95% polarized or about 100% polarized. Lower or higher percent polarized light can be used depending on the yield of chlorine dioxide produced. The angle of polarized light may also vary relative to unpolarized light source. The intensity of the radiation can vary from about 1,000 microwatts/cm² to about 60,000 microwatts/cm².

[0036] Methods disclosed herein can be carried out in situ and ex situ. Furthermore, the chlorine dioxide formed need not be separated from the reaction mixture; however, the entire reaction mixture, including the chlorine dioxide formed, may in most instances, be used as a whole since the other components of the reaction do not exert a detrimental influence on the application properties. Thus, the chlorine dioxide containing reaction product obtained as a result of the polarized radiation may be expelled from the reaction space and conveyed to a place of use, or, if desired, after completion of the reaction, the reaction mixture may be passed through water to form dissolved chlorine dioxide or chlorous acid.

[0037] One or more UV lamps can be positioned such that there exists a time interval between irradiations. The one or more UV lamps can be turned off and on such that there exists a specific period during which there is no irradiation. This cycle of irradiation followed by a pause, enhances the yield of chlorine dioxide. This cyclical irradiation pattern is established by configuring one or more lamps serially or in parallel configuration, such that an incoming flow of precursor is exposed to the one or more lamps in a serial fashion with time intervals or by turning on and off the UV lamps in a periodic mode.

[0038] Chlorine dioxide (ClO₂) production is enhanced by use of an electromagnetic field (EMF) or electromotive force. In an aspect, the electromagnetic field is present during ultraviolet (UV) radiation-based production of chlorine dioxide. The EMF is believed to favor the reaction that results in the formation chlorine dioxide from the starting materials, e.g. chlorine and oxygen.

[0039] A polarizing screen may be a linear reflecting polarizer screen, e.g., a 90° linear polarizer that functions like a conventional absorption polarizer, except that it reflects (instead of absorbs) substantially all light that does not pass though it. The 90° reflecting polarizer screen transmits substantially all light waves polarized to 90° (i.e., "vertically" polarized light) and reflects substantially all light waves polarized to 0° (i.e., "horizontally" polarized light). Polarizer may be made of any suitable reflecting polarizing material, such as double brightness enhancement film ("DBEF"), material obtained from Minnesota Mining and Manufacturing Company (3M Inc.). [0040] A suitable polarizer also includes a high transmittance-high efficiency linear polarizer that has about 38% transmittance for unpolarized light. Commercial-quality film polarizers available in medium gray (25% transmission) and medium brown (22% transmission). Polarization efficiency is over 90%, preferably over 95%, and more preferably over 99%. Extinction is described generally as a polarizing filter's ability to absorb polarized light that has an orientation 90° to the polarizer's axis of polarization.

[0041] In an embodiment, reaction geometry of selected species (e.g., Cl₂ and O₂) can be controlled by using polarized light. It is possible that one of the reactants is generated in a photodissociation process. Another molecular reactant may be excited in a specific rovibrational state. For example, an attacking oxygen or a chlorine atom is generated in the photodissociation/photolysis in the UV range (e.g., about 100-400 nm, or about 200300 nm, or about 250-280 nm; or about 280-355 nm). For example, in an embodiment, chlorine atom is formed in the photolysis of Cl₂ at 355 nm. Polarized UV excitation provides an optimal reaction geometry for the formation of ClO₂ molecule from its reacting constituents.

[0042] Atomizing (dispersion into small size droplets) a chlorate solution or any suitable reaction mixtures prior to or contemporaneously irradiating by UV, results in an increased production of chlorine dioxide. Atomizing or spraying or vaporizing can be performed by any suitable equipment such as an atomizer, a container equipped with a spray head and the like.

[0043] The invention will now be described by several examples, it being understood that this information is furnished by way of illustration only and not by way of limitation.

[0044] EXAMPLE 1: Production of chlorine dioxide. NaClO₃ solutions are exposed to radiation from an ultraviolet light source of about 4000 m watts/cm² at one inch and peak wavelength of 254 nm in the presence of carbon as a catalyst. Chlorine dioxide is formed as determinable by spectrographic absorbance.

[0045] EXAMPLE 2: Production of chlorine dioxide in a reactor chamber.

This experiment can be carried out in the reactor or apparatus shown in FIG. 1. [0046] Space 5 of the reactor vessel 1 is flushed with oxygen, introduced through inlet 2 to replace the air atmosphere in the reactor. A 1% w/v solution of sodium chlorate in water is thereafter introduced into the chamber space through inlet 2 and the quartz lamp is switched on to expose the solution to ultraviolet radiation. The radiation emitted by the lamp has a constant intensity of 4,000 m watts/cm² at 254 nanometers at 1 inch. The reference to "1 inch" indicates the distance from the center of illumination where the rated intensity is measured. The solution is subjected to radiation in the presence of a carbon catalyst. Chlorine dioxide is detected in the solution after 10 seconds of exposure to the radiation by absorbance peak and titration. No significant amount of chlorine is detected. The reaction mixture within the chamber space is then removed by flowing oxygen gas through the chamber and the expelled gas mixture is collected through the outlet 3 and analyzed for content. The analysis is performed by spectrophotometry and correlated with amphoteric titration. The presence of chlorine dioxide is again established by observing the distinct absorbance peak of chloride dioxide. The results are confirmed by titration. The procedure is repeated several times with different concentrations of chlorite in the solution to oxygen gas to determine the most favorable conditions and also to establish the range of concentrations that provides chlorine dioxide free of unreacted chlorine. [0047] Constant wavelengths of 254 nanometers are maintained during the experiments without ozone producing interfering wavelengths. If desired, several lamps may be used as a UV radiation source. In one series of experiments, two lamps were used, each being rated at 20,000 m watts/cm² at 1 inch. However, it is possible to use lamps rated at 4,000 m watts/cm² or less, in which event, up to 10 or even more lamps may be used. The lamps may also be coated with Teflon^® or any suitable anti-corrosive layer.

[0048] Removal of ClO₂ gas from solution as a pure gas can be accomplished by a stream of air (positive or negative), and the removed chlorine dioxide gas can be readily used to or temporarily stored in cold water for later use. Removal of ClO₂ gas can also be performed by applying continuous or periodic vacuum in the reaction chamber. [0049] Mercury vapor lamp (500Ov; 40 milliamp current) can also be used and maintained at 32 ⁰C or any suitable ambient temperature and pressure. All wetted parts are protected by inert materials to ClO₂ and UV radiation, and the reaction surface is reactive to volume of flow or contaminant.

[0050] Exposure to irradiation time is directly proportional to concentration of [ClO₂] + [H⁺] or [ClO₃] + [H⁺] and wattage of radiation. [0051] In an embodiment, potassium chlorate is suitable for chlorine dioxide generation

[0052] While embodiments have been illustrated and described in the drawing and foregoing description, such illustrations and descriptions are considered to be exemplary and not restrictive in character, it being understood that only illustrative embodiments have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected. The applicant has provided description and figures which are intended as illustrations of embodiments of the disclosure, and are not intended to be construed as containing or implying limitation of the disclosure to those embodiments. Several advantages of the present disclosure arise from various features set forth in the description. It will be noted that alternative embodiments of the disclosure may not include all of the features described yet still benefit from at least some of the advantages of such features. Those of ordinary skill in the art may readily devise their own implementations of the disclosure and associated methods, without undue experimentation, that incorporate one or more of the features and/or steps of the disclosure and fall within the spirit and scope of the present disclosure and the appended claims.

Claims

1. A method of producing chlorine dioxide, the method comprises introducing a solution of chlorate or chlorite into a reaction chamber and subjecting the solution to UV radiation in the presence of a catalyst.

2. The method of claim 1 , wherein the chlorate is NaClO₃ and the chlorite is NaClO₂.

3. The method of claim 1, wherein the catalyst is a carbon catalyst.

4. The method of claim 1, wherein the chlorate or chlorite concentration is from about 10% w/v to about 50% w/v.

5. The method of claim 1, wherein the chlorine dioxide generated is less than about 10% w/v.

6. The method of claim 1 , wherein the production of chlorine dioxide is performed in situ.

7. The method of claim 1 , wherein the ultraviolet radiation is provided by an ultraviolet generating lamp coated with an anticorrosive material.

8. The method of claim 1 , wherein the UV radiation comprises a wavelength between 180-300 nm.

9. The method of claim 1 , wherein the UV radiation is about 2,000-20,000 m watts/cm².

10. The method of claim 7, wherein the anticorrosive material is polytetrafluoroethylene (PTFE).

11. The method of claim 1 , wherein the pH is maintained in a range of about pH 3.5 to about pH 5.0.

12. The method of claim 1 , further comprising the step of removing the chlorine dioxide from the reaction chamber.

13. The method of claim 1 , wherein the chlorine dioxide produced is used along with a solution from the reaction chamber.

14. The method of claim 1 , wherein the solution of chlorate or chlorite is an aqueous solution.

15. The method of claim 14, wherein the method further comprising contacting the aqueous solution of chlorate or chlorite with carbon dioxide gas.

16. The method of claim 15, wherein carbon dioxide gas is bubbled into the solution.